Technical Field
Embodiments are directed to pressure transducers and calibration instruments.
Description of the Related Art
Generally described, Bourdon tubes are tubes that flex radially, by coiling and uncoiling, in response to pressure changes between the tube and it surrounding environment. A sensor, such as a resonant sensor, may be attached to a closed end of the tube so that as the tube flexes, the movement imparts a force on the resonant sensor. The frequency at which the resonant sensor resonates due to the force is indicative of the pressure in the tube.
Typically, Bourdon tubes are made from a metal material. The metal material, however, has been shown to cause hysteresis, a phenomenon that can affect the true measurement of the Bourdon tube. In particular, hysteresis occurs due to metal Bourdon tubes retaining some energy between measurements. For instance, the metal Bourdon tube may retain deformations for a period of time after a measurement has been obtained. Thus, during a subsequent measurement that occurs during the period of time in which the Bourdon tube is deformed, the deformity affects the measurement, thereby contributing error to the subsequent measurement. Although metal is described as causing hysteresis, adhesive materials, such as epoxy, which bond the metal Bourdon tube to various components within a Bourdon tube pressure transducer, can also cause hysteresis, as can stress in the mounting or structural materials throughout the device.